Understanding the Blueprint of Life

In February of 2001, scientists delivered a complete map of the human genome. In fact, two competing teams of scientists published two all-but-identical genome maps in different journals in the same week. This remarkable news made headlines all over the world because it meant that finally disease researchers would have a full account of every base pair in the human genetic code on which to focus their search for genetic disease. Just as remarkable, though, was the fact that the two teams, one government-led and one privately owned, finished their genome maps a full five years ahead of schedule.

The race to be the first to map the human genome revolutionized the science of genetics. Only a decade ago, scientists using traditional gene sequencing methods mapped just a few hundred base pairs a day. Then automation changed all that. The government-led Human Genome Project (HGP) poured millions of dollars into computers that could read a thousand letters a second. But even this highly advanced technique was conventional compared to the competing team's method.

The private biotech firm Celera changed the rules of gene sequencing. The company's so-called "shotgun" technique allowed Celera to sequence the entire genome in eight months -- a feat that took the HGP several years to achieve. As its name suggests, however, the shotgun technique is less than meticulous. While the HGP's traditional method kept track of where each decoded segment came from, Celera's method required that all of the randomly separated pieces of the genome be painstakingly reassembled. This not-inconsequential step took Celera supercomputers another seven months to achieve. Even so, the total time it took the company to map the genome was faster than anyone could have imagined.

The resulting genome maps have already proven to be far more than a detailed list of the three billion letters that make up our genetic code. Scientists are using them to identify and better understand the tiny functional portion of the genome: our genes.

Watch the excerpt from Nova’s Cracking the Code of Life and answer the following questions:

  1. What is a genome?
  1. How is the human genetic code represented?
  1. How long is the code?
  1. What has the human genome project revealed about the difference between humans and bananas?
  1. How did scientists originally map the genome? How do they currently map it?
  1. What percent of your DNA is actually composing active genes?
  1. How does Dr. Lander compare our DNA to a Boeing 777? How is the human genome project specifically like a parts list?
  1. Why do scientists compare the DNA of bananas, worms, fruit flies, and humans? How can this information be helpful?

Explore Journey Into DNA. Try to answer the questions as you go…Click through the flash animation by hitting the magnifying glass.

  1. How many cells are in the human body?
  2. What organelle is called the control center of the cell?
  3. How many chromosomes are inside the cell’s nucleus?
  4. How many genes are stored in these chromosomes?
  5. Draw a chromosome.
  6. How many letters (bases) is a typical gene?
  7. If you could spread it out, how long would your DNA be?
  8. To fit inside of the cell DNA is wrapped around histones. Histones are an example of what kind of molecule?
  9. In DNA, A always pairs with ______and C always pairs with ______.
  10. DNA is made up of repeated units. These units contain sugar, phosphate, and bases. What are these units called?
  1. How many atoms are in just one nucleotide?

Explore Exploring a Stretch. Try to answer the questions as you go…

  1. Reveal the on/off switch. Use the explanations at the bottom of the page to explain what an on/off switch is. Why are they necessary?
  1. Reveal the start codon. What is a start codon?
  1. Reveal the stop codon. What is a stop codon?
  1. Reveal the introns and exons. What is the difference between an intron and exon?
  1. Are introns or exons ‘spliced out’ (or removed) from the sequence?
  1. Reveal the ancient code. How is it possible for humans, yeast, and pufferfish to have similar sections of code?
  1. Reveal the sites of variation. How similar are two humans?
  2. Reveal the gene. What is a gene?
  3. What is the main focus of geneticists now that the human genome has been decoded?

Complete the following conclusion questions:

  1. What was the purpose of the human genome project?
  2. What has it revealed about similarities between humans (and between humans and other organisms)?
  3. How long is the human genome (how many letters)?
  4. What are genes?
  5. Is every letter of the genome included in our genes?
  6. What can scientists do now that they know the sequence of the human genome?
  7. What is one disease that can be traced back to our genome?